1. Field of the Invention
The present invention relates to a hydrogen sensor mounting structure for use in a fuel cell vehicle, in which the hydrogen sensor is located above a fuel cell system installed under a floor panel.
This application claims priority on Japanese Patent Application No. 2005-153742 filed on May 26, 2005, and incorporates the content thereof herein in its entirety.
2. Description of Related Art
Fuel cell systems that can be incorporated in a fuel cell vehicle such as a fuel cell automobile include, for example, a system that supplies an oxidant gas to a cathode of the fuel cell while supplying a fuel gas to an anode of the fuel cell, to generate an output electric power through an electrochemical reaction of the gases.
With regard to vehicles with such a fuel cell, a technique for safety assurance is known, for example, for detecting that there is no leakage of hydrogen supplied to the fuel electrode of the fuel cell.
For example, referring to FIG. 4, a fuel cell vehicle 1 has a floor panel 5 with a central portion thereof protruding into the inside of a cabin, to thus form a center tunnel 6, and a technique is studied in which a hydrogen sensor 4 (see FIG. 5) is mounted above a piping/wire harness 3 running through the center tunnel.
In connection with this, Japanese Unexamined Patent Application, First Publication No. 2003-252252 proposes a technique of forming an additional protruding portion in an upper portion of the floor tunnel provided on the floor panel, which protrudes further toward the upper portion, for accommodating the hydrogen sensor in the protruding portion, and disposing the fuel cell unit and the piping under the hydrogen sensor, so as to prevent water or mud splashing up from the road from directly hitting the hydrogen sensor.
Such conventional techniques, however, have the following drawbacks.
Referring to FIG. 6, when the hydrogen sensor 4 is disposed under the center tunnel 6 (outside the cabin), not only a gap la for preventing interference by the center tunnel 6 with the fuel cell device 2 and the piping/wire harness 3 disposed under the center tunnel 6, but also a space for accommodating the hydrogen sensor 4, corresponding to the height 1b thereof, have to be taken into consideration when forming the center tunnel 6. This leads to an increase in the height required for the center tunnel 6, thus giving rise to restrictions in layout designing in a vertical space, for securing the necessary height.
Furthermore, when providing a protection cover (not shown, see FIG. 3) that protects a detecting portion 8 from flying stones or splashing water, because an entirety of the hydrogen sensor 4 is exposed outside the cabin, a space for attaching the cover that encloses the entire hydrogen sensor 4 has to be secured under the center tunnel 6, which also results in restriction of freedom in arranging the hydrogen sensor 4 and the protection cover.
In addition, as is apparent from FIG. 6, the detecting surface 8 of the hydrogen sensor 4 can only be located lower than the hydrogen sensor mounting position on the center tunnel 6 (ceiling portion of the center tunnel), at least by the height of the sensor main body 7 of the hydrogen sensor 4. Accordingly, even when hydrogen is present under the center tunnel 6, if the hydrogen is floating in an upper position (region A) than the detecting surface 8 of the hydrogen sensor 4 because of the lighter specific gravity of hydrogen, the hydrogen sensor 4 may not detect the hydrogen, which leads to degradation of detecting accuracy.
Furthermore, in the configuration of mounting the hydrogen sensor 4 under the center tunnel 6, the fuel cell device 2 and the piping/wire harness 3 located thereunder hinder the work of mounting the hydrogen sensor 4. In order to perform maintenance work for the hydrogen sensor 4 the fuel cell device 2 and the piping/wire harness 3 have to be removed, which complicates the work of removing and mounting the hydrogen sensor 4, thus imposing a heavier labor burden.
In view of the foregoing, it is an object of the present invention to provide a hydrogen sensor mounting structure for a fuel cell vehicle that offers higher layout designing freedom, prevents degradation of detecting accuracy, and allows easy removal and mounting of the hydrogen sensor.